1. Field of the Invention
The present invention relates to an optical disk on which address information is recorded as wobbles of a recording track, an optical disk apparatus that records and reproduces information on and from the optical disk, and a method of recording information.
2. Description of the Related Art
DVD-RAMs and DVD RWs are known as rewritable optical disks. These optical disks have an information recording layer formed on a transparent substrate. Laser light is condensed on the information recording layer to record and reproduce information. Further, as means for recording and reproducing information, the information recording layer of the optical disk has a guide groove often simply called a groove. Information is recorded and reproduced along the guide groove. Furthermore, physical addresses are formed along the guide groove to identify spatial positions at which recording or reproduction of information is carried out.
In a DVD-RAM, a technique called land and groove recording is used as means for increasing density. In the DVD-RAM, information is recorded both on a groove, which is a concave portion of the guide groove, and on a land, which is a convex portion of the guide groove. This serves to reduce the intervals at which data is recorded in a radial direction, to increase a recording capacity. On the other hand, the physical addresses are formed of intermittent concaves and convexes on the substrate called prepits. The guide groove is discontinued in these physical address areas.
In contrast, in a DVD-RW, information is recorded only on the groove, which is the concave portion of the guide groove. On the other hand, as means for forming physical addresses, modulation of groove wobbles (hereinafter referred to as “wobble modulation”) is used in which the guide groove is slightly vibrated in the radial direction. The physical addresses formed using the wobble modulation do not block a recording track (guide groove). Accordingly, these physical addresses have the advantages of increasing an area in which user information is recorded, that is, improving a format efficiency, and making the optical disk easily compatible with reproduction-exclusive media.
Thus, for an optical disk apparatus that records information on an optical disk having address information based on the wobble modulation, it is necessary to synchronize the phase of a wobble address with the phase of data to be recorded in a sector or the like during information recording. However, there may be a difference in phase between the wobble address and the data to be recorded for some reason. When data is recorded on the optical disk while there remains a phase difference, it may be difficult to reproduce the recorded data. Jpn. Pat. Appln. KOKAI Publication No. 2002-32962 describes a technique for varying the frequency of a recording clock depending on the phase difference.
With this patent document, if there is a difference in phase between a recorded stream and the wobble address, the recording clock frequency is controlled to remove the phase difference. Thus, disadvantageously, jitter may occur in the recording clock, which degrades recording signals.